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11.
Zhiying Liu Zhen Zhang Tianyu Zhang Ruofan Gao Xiliang Li 《Grass and Forage Science》2019,74(3):427-436
Limited plant stem elongation is hypothesized to be the primary cause of decreased plant growth in response to long‐term heavy grazing (LHG). However, it remains largely unknown how LHG‐induced changes in stem elongation are mediated by internode traits. Accordingly, we experimentally investigated the effects of LHG (defined as twice the stocking rate recommended by the local government) on plant stem elongation and internode allometry in Leymus chinensis in Xilinhot, Inner Mongolia, China. Plant size and internode traits, including internode length (IL), internode diameter (ID), and internode number (IN), from plant individuals were measured according to their phytomer position from base to apex. The results revealed that IN and their distributions were changed in response to LHG. Although LHG negatively affected IL and ID of each L. chinensis internode from base to apex and eventually stem length, the plasticity index of IL and ID increased initially and then decreased from the lowermost to the uppermost internode in response to LHG. These contrasting responses of internode traits were result of allometry between internode traits determined by both LHG and internode position. Ultimately, IL and IN were identified to be key traits influencing stem length reduction under LHG conditions and explaining 52.51% and 47.49% of variation in stem length, respectively. Overall, our findings suggest that the limitation of L. chinensis stem elongation induced by LHG is mediated by the plasticity and allometry of internode traits. This result emphasizes the sensitivity of individual plants to LHG and is potentially valuable for optimal grassland management. 相似文献
12.
Under extensive grazing, a mosaic pattern of frequently defoliated short patches and rarely defoliated tall patches is often formed. The agronomic and ecological consequences of this patch‐grazing pattern strongly depend on its stability between successive years. We assessed patch structure and temporal stability under three intensities of cattle stocking (moderate, lenient and very lenient) in a cattle grazing experiment established in 2002. Aerial images of the whole area taken in 2005, 2010, 2013 and 2015 were classified into short and tall patches using random forest classification. These were complemented by annual sward height measurements (2007‐2017) at 10 permanent plots per paddock, which were classified into sward height classes. The mean proportion (0.72, 0.32, 0.19) and size of short patches decreased with stocking intensity, while size of tall patches increased. Inter‐annual stability depended on patch type and stocking intensity and was particularly high for the respective dominant patch type. Of the short patch area in 2015, 0.62, 0.29 and 0.30 were classified as short in all four aerial images under moderate, lenient and very lenient grazing, respectively; the corresponding proportions for tall patches were 0.10, 0.53 and 0.65. Our results imply that short and tall patches experience persistent differences in local grazing intensity over extended periods. The long‐term effects of this heterogeneity on soil properties and vegetation composition need to be monitored to assess agronomic sustainability and ecological potential of patch‐grazed pastures. 相似文献
13.
Helga Pülzl Daniela Kleinschmit Bas Arts 《Scandinavian Journal of Forest Research》2014,29(4):386-393
The term bioeconomy and closely related notions like bio-based economy or knowledge-based bioeconomy (KBBE) are increasingly used by scientists and politicians in the last years. It does therefore have the potential of becoming an influential global discourse. Its role is however so far unclear. The general assumption that guides this paper is that discourses, resulting ideas and arguments are generally said to have performative power. They shape actors' views, influence their behaviour, impact on their beliefs and interests and can cause institutional change in a given society. Thus, the aim of this paper is twofold: first, it aims to analyse whether the ideas used in a bioeconomy discourse differs from those in other global meta-discourses of the last decades affecting forest discourses, such as the ecological modernization discourse or the sustainable development discourse. Second, this paper aims to analyse whether and how the bioeconomy discourse has started (or not) to reshape or overshadow the “classical” forest discourses, such as sustainable forest management, forest biodiversity or forest and climate change. 相似文献
14.
During the last decade there has been a number of conflicts in relation to the trade of salmon in the EU. A 5-year agreement between Norway and the EU including an import constraint and a voluntary minimum import price agreement for exporter just expired, with a 13% tariff to be paid by exporters that do not accept the agreement. A year after the agreement expired, there are again calls for safeguard measure to protect EU-producers. We investigate the expected welfare effects of this tariff by analyzing a general equilibrium demand curve. In contrast to earlier studies we use a derived demand approach rather the consumer demand as most available data are at the trade level. The results indicate that only Norwegian exporters are beneficial to target for EU producers. The total welfare effect of the tariff depends critically on the supply structure of EU and Norwegian salmon. 相似文献
15.
Island ecosystems differ from mainland ecosystems in their long-term isolation. On Sado Island, Japan, cattle grazing in the past gradually changed forests into grasslands, thereby altering the diversity of indigenous insects. We compared ground-dwelling beetle diversity on Sado Island to that on the nearby mainland. Contrary to previous reports, the island isolation effect resulted in lower γ and β diversity than on the mainland, because of the low species richness of beetles with low dispersal abilities. Few flightless beetles could invade Sado Island, even when the beech forests on the island were relatively adjacent to those on the mainland. Such a history of ecosystem formation could be the general pattern for continental-island mountain forests that were never connected to those of the mainland. We did not observe low α diversity of ground-dwelling beetles, suggesting that the cattle grazing history of the island has not changed environmental conditions for ground-dwelling beetles enough to reduce their diversity. In addition, cattle grazing increases the abundance of merdivorous insects by increasing the abundance of their food resource. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
《Land Degradation u0026amp; Development》2017,28(7):2030-2038
Rangelands are vital for wildlife conservation and socio‐economic well‐being, but many face widespread degradation because in part of poor grazing management practices. Planned grazing management, typically involving time‐controlled rotational livestock grazing, is widely touted as a tool for promoting sustainable rangelands. However, real‐world assessments of its efficacy have been lacking in communal pastoral landscapes globally, and especially in Africa. We performed landscape‐scale assessment of the effects of planned grazing on selected vegetation, wildlife, and cattle attributes across wide‐ranging communally managed pastoral rangelands in northern Kenya. We found that planned grazing enhanced vegetation condition through a 17% increase in normalized difference vegetation index, 45–234% increases in herbaceous vegetation foliar cover, species richness and diversity, and a 70% reduction in plant basal gap. In addition, planned grazing increased the presence (44%) and species richness (53%) of wild ungulates and improved cattle weight gain (>71%) during dry periods when cattle were in relatively poor condition. These changes occurred relatively rapidly (within 5 years) and despite grazing incursion incidents and higher livestock stocking rates in planned grazing areas. These results demonstrate, for the first time in Africa, the positive effects of planned grazing implementation in communal pastoral rangelands. These improvements can have broad implications for biodiversity conservation and pastoral livelihoods. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
17.
The impact of manipulating ruminal fill (RF) on intake rate of herbage and grazing dynamics was measured with three rumen‐cannulated beef heifers grazing Bermudagrass pastures individually. The treatments compared were removal of proportions of rumen contents of 0 (treatment RF0), 0·33 (treatment RF33), 0·66 (treatment RF66) and 1·00 (treatment RF100). Treatments were randomly applied in a 3 × 4 Youden‐square design. The rumens were emptied before and after planned grazing sessions (30 min) to set up the treatments, and to estimate intake rate and bite mass, respectively. Measurements were made of bite rate, bites per feeding station, feeding stations per minute, intake per feeding station, time per feeding station, eating and searching step rates and times. Apparent bite area and area grazed per feeding station were calculated. Ruminal fill affected short‐term intake rate and changed grazing dynamics. As RF increased, step rates, searching times, bite mass, apparent bite area, bites per feeding station, area grazed per feeding station, time per feeding station and intake per feeding station decreased (P < 0·01) while step times, eating step rates and bite depth increased (P < 0·01). The results of the present study indicate that RF is an important factor governing the intake characteristics and behaviour of grazing beef heifers. 相似文献
18.
辽宁东部山地混牧林可控阈值研究 总被引：3，自引：0，他引：3
辽东山区的林业和牧业一直是既互相依存又互相矛盾的两个行业，混牧林业的提出为解决这一问题提供了科学的依据。通过4年时间的定位观测及调查研究。对辽宁省混牧林业的现状，存在问题以及发展趋势等进行了系统研究，针对该区域森林生态环境的基本特征。制定出科学、简明、具有可操作性的林牧结合阈值：(1)幼林林分伤害指数临界阈值不能高于50；(2)截取利用牧草生物量(地上部分)50％为最佳值；(3)选择混牧林的坡度应小于30度。A层土容重不应大于1．3g。 相似文献
19.
《Strength and Conditioning Journal》2020,73(1):53-60
Knowledge of herbivory tolerance of dominant plant species and their responses to varying grazing intensity is required for sustainable grazing management in semiarid rangeland ecosystems. In a field experiment, we studied the effects of simulated grazing 0%, 30%, 50%, and 80% leaf removal (control, partial, intermediate, and heavy leaf removal) of three dominant perennial legumes: Astragalus cyclophyllon, Astragalus effuses, and Hedysarum criniferum in semiarid rangelands of southwestern Iran for 2 yr and tested 1) differential herbivory tolerance in terms of regrowth ability of belowground and aboveground biomass (AGB), fecundity, and nonstructural carbohydrate reserves; and 2) trade-off between forage quantity and quality—less defoliated plants produce larger amount of biomass with less forage quality and vice versa. The results showed a reduction in AGB and reproduction in each of the three plants. However, three forbs exhibited some sort of variations in shoot and root growth, reproduction and forage quality under intermediate and heavy leaf removal. Leaf removal in individuals of A. effusus and H. criniferum are more likely to compensate for tissue loss by allocating the available resources to the expansion of root biomass, at the cost of AGB and reproductive effort. Leaf removal also led to an increase in forage quality in each of the three forb species, depending on the level of height removal. The control plant had a higher amount of biomass production and lower amount of crude protein compared with heavy leaf removal treatments (i.e., 80%), by contrasting responses of acid detergent fiber and neutral detergent fiber, indicating a trade-off between forage quality and forage quantity. The results indicate that there is a balance among forage quantity, quality, and regrowth ability of belowground and aboveground tissues in intermediate leaf removal treatments of these forb species. This balance is used to develop principles for grazing management of steppe rangelands because such a regime meets different criteria including forage quantity, quality, and nonstructural carbohydrate reserves. 相似文献
20.
发达国家和发展中国家生态补偿机制比较分析 总被引：2，自引：1，他引：2
刘平养 《干旱区资源与环境》2010,24(9)
生态补偿是处理环境保护和经济发展之间的矛盾、保障环境保护领域的社会公平的重要手段。通过比较研究发现,发达国家的生态补偿机制基于完善公共财政体系,直接以降低保护区的经济活动强度为导向;发展中国家的生态补偿机制则更倾向于通过自然资源的可持续开发来补偿保护地的发展机会损失。这两类生态补偿机制在实际应用中都存在一定的局限性。研究认为,我国应当在借鉴发达国家和发展中国家经验的基础上,以降低保护地经济活动强度为导向,结合我国的城市化进程,建立适合我国国情的生态补偿机制。 相似文献